David Szczesniak DavidSzczesniak

## deny_cron_at.txt
By default, everyone is allowed to create cron and at jobs.
However, users can be denied if explicitly listed in one of the .deny files: at.deny or cron.deny.
These are both located in /etc by default.

## at_batch.txt
\!h at format

in the command line type:
at <time> <date> e.g noon tomorrow or 11am june 26

this opens an at> prompt. Type in commands to be executed.

CTRL+D to end job definition - the new job is now set

atq - to list jobs

## system_crons.txt
crontab -e
5 20 * * 1-5 root /usr/sbin/backup.sh

\!h Seven fields:

- Minute (0-59): 5 past the hour
- Hour (0-23): 8pm
- Day of the Month (0-31): any day
- Month (1-12): any month
- Day of the Week (0-7): Mon-Friday

## match_variables.pl
# The part of the string that matches the pattern is automatically stored in $&

if ("Hello there, neighbor" =~ /\s(\w+),/) {
  print "That actually matched '$&'.\n";
}

# In the above example, the part that matched was " there," (a space, a word, and a comma).
# In comparison, capture $1 would have just the five-letter word.
# Whereas, $& has the entire matched section.

## noncap_parentheses.pl
# Example:

# Before - bronto is $1 and what we want is $2. This will get confusing in more complicated patterns
if ((/bronto)?saurus (steak|burger)/) {
  print "Fred wants $2\n";
}

# After - now using noncapturing parentheses around bronto
if (/(?:bronto)?saurus (steak|burger)/) {
  print "Fred wants $1\n";

## named_captures.pl
if (/bronto)?saurus (steak|burger)/ {
  print "Antisa wants a $2\n";
}

# Even if bronto is not there, its part of pattern that goes into $1.

# You can refer back to a labeled group using \g{label}:
my $names = 'Fred Flintstone and Wilma Flintstone';

if ($names =~ m/(?<last_name>\w+) and \w+ \g{last_name}/) {

## char_interpret.pl
# /a - use the ASCII interpretation

# /u - use the Unicode interpretation

# /l - respect the locale

# A single /a modifier affects the character class shortcuts,
# but having two /a modifiers also tells Perl to use ACII-only case-folding.

\!h # Some examples:

## x_modifier.txt
\!h # Example, allows for code spacing:

/-?[0-9]+\.?[0-9]/ # - without

/ -? [0-9] + [0-9]* /x # - with

## unicode_props.pl
\!h # To match a particular property, you put the name in \p{PROPERTY}

# Example - to match any sort of space, use the 'Space' property:

if (/\p{Space}/) {
  print "The string has some whitespace.\n";
}

# The above is slightly more expansive than \s as it matches more properties, like NEXT LINE or LINE TABULATION (vertical line).

## char_class_shortcuts.pl
\!h # Some basic shortcuts:

# \s meaning any whitespace

$_ = "fred \t \t barney";
if (/fred\s+barney/) {
  print "It matched!\n"
}

# \h can be used for horizontal whitespace only
	By default, everyone is allowed to create cron and at jobs.
	However, users can be denied if explicitly listed in one of the .deny files: at.deny or cron.deny.
	These are both located in /etc by default.
	\!h at format

	in the command line type:
	at <time> <date> e.g noon tomorrow or 11am june 26

	this opens an at> prompt. Type in commands to be executed.

	CTRL+D to end job definition - the new job is now set

	atq - to list jobs
	crontab -e
	5 20 * * 1-5 root /usr/sbin/backup.sh

	\!h Seven fields:

	- Minute (0-59): 5 past the hour
	- Hour (0-23): 8pm
	- Day of the Month (0-31): any day
	- Month (1-12): any month
	- Day of the Week (0-7): Mon-Friday
	# The part of the string that matches the pattern is automatically stored in $&

	if ("Hello there, neighbor" =~ /\s(\w+),/) {
	print "That actually matched '$&'.\n";
	}

	# In the above example, the part that matched was " there," (a space, a word, and a comma).
	# In comparison, capture $1 would have just the five-letter word.
	# Whereas, $& has the entire matched section.
	# Example:

	# Before - bronto is $1 and what we want is $2. This will get confusing in more complicated patterns
	if ((/bronto)?saurus (steak\|burger)/) {
	print "Fred wants $2\n";
	}

	# After - now using noncapturing parentheses around bronto
	if (/(?:bronto)?saurus (steak\|burger)/) {
	print "Fred wants $1\n";
	if (/bronto)?saurus (steak\|burger)/ {
	print "Antisa wants a $2\n";
	}

	# Even if bronto is not there, its part of pattern that goes into $1.

	# You can refer back to a labeled group using \g{label}:
	my $names = 'Fred Flintstone and Wilma Flintstone';

	if ($names =~ m/(?<last_name>\w+) and \w+ \g{last_name}/) {
	# /a - use the ASCII interpretation

	# /u - use the Unicode interpretation

	# /l - respect the locale

	# A single /a modifier affects the character class shortcuts,
	# but having two /a modifiers also tells Perl to use ACII-only case-folding.

	\!h # Some examples:
	\!h # Example, allows for code spacing:

	/-?[0-9]+\.?[0-9]/ # - without

	/ -? [0-9] + [0-9]* /x # - with
	\!h # To match a particular property, you put the name in \p{PROPERTY}

	# Example - to match any sort of space, use the 'Space' property:

	if (/\p{Space}/) {
	print "The string has some whitespace.\n";
	}

	# The above is slightly more expansive than \s as it matches more properties, like NEXT LINE or LINE TABULATION (vertical line).
	\!h # Some basic shortcuts:

	# \s meaning any whitespace

	$_ = "fred \t \t barney";
	if (/fred\s+barney/) {
	print "It matched!\n"
	}

	# \h can be used for horizontal whitespace only